Refrigerant circuit
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Solution Overview
Problem
Heat transfer from the heat exchanger body to the refrigerant, particularly CO2, flowing and sublimating in the heat exchanger channel, limits the heat absorption of the heat exchanger body in refrigerant circuits.
Innovation Solution
A mixture of refrigerant and a functional conveying agent flows through the heat exchanger channel, ensuring the functional conveying agent remains liquid during sublimation, enhancing heat transfer by wetting the refrigerant and the heat exchanger body, and a lubricant separator is used to manage lubricant circulation and prevent blockages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pure refrigerant (CO2) flows through the heat exchanger channel and sublimates, then the refrigerant absorbs heat from the heat source, but the heat transfer from the heat exchanger body to the refrigerant is limited
Solution Approach 1:
A functional conveying agent is introduced as an intermediary substance that mixes with the sublimating refrigerant. This agent remains liquid during sublimation and enhances heat transfer by wetting both the refrigerant and the heat exchanger body walls, thereby improving the heat transfer coefficient and overall heat absorption efficiency without fundamentally changing the sublimation process
Solution Approach 2:
The physical and chemical parameters of the refrigerant are modified by adding a functional conveying agent. This changes the heat transfer characteristics of the refrigerant mixture, allowing for improved heat transfer from the heat exchanger body to the refrigerant while maintaining the sublimation mechanism. The mixture ratio and composition are optimized to achieve enhanced heat transfer performance
2Productivity
If a functional conveying agent is added to improve heat transfer, then heat absorption increases, but the operating conditions and safety of the refrigerant circuit may be affected
Solution Approach 1:
The parameters of the functional conveying agent (composition, concentration, physical properties) are carefully selected and optimized to ensure that the mixture maintains stable operating conditions. The agent is chosen to be compatible with the refrigerant circuit materials and to not significantly alter the triple point or critical properties of the refrigerant system, thereby maintaining reliability while improving heat transfer
Solution Approach 2:
The functional conveying agent is selected to be chemically stable and non-reactive under operating conditions, effectively making it a stable additive that does not degrade or cause harmful reactions. This ensures long-term reliability of the system while achieving improved heat transfer performance
3Reliability
If lubricant is removed from the refrigerant circuit using a lubricant separator, then blockages in the heat exchanger channel are prevented, but the lubricant must be managed and recirculated
Solution Approach 1:
A lubricant separator is introduced to extract and remove lubricant from the refrigerant circuit at a specific location. This separates the lubricant management function from the main refrigerant flow, preventing blockages in the heat exchanger channel while allowing the lubricant to be collected and recirculated through a dedicated pathway, thus improving reliability without excessive complexity
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution improves heat absorption by the sublimating refrigerant and increases the efficiency of heat transfer between the refrigerant and the heat exchanger body, while maintaining the operating conditions and environmental compatibility of the refrigerant circuit.
Implementation Method 1
improves heat transfer in the heat exchanger channel (36) between the sublimating refrigerant and the heat exchanger body (40) having the heat exchanger channel (36)
Implementation Method 2
improves heat transfer between them by wetting, on the one hand, the sublimating refrigerant and, on the other hand, the walls of the heat exchanger body enclosing the heat exchanger channel
Implementation Method 3
the refrigerant, after leaving the expansion element (34), falls below the triple point in the downstream heat exchanger channel (36) and sublimates, thereby absorbing heat from a heat source (28)
Implementation Method 4
a refrigerant compressor (12) which compresses refrigerant to a high pressure level which is above the triple point of the refrigerant
Data Source
Figure 1
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AI summary
To improve the heat transfer from the heat exchanger body to the sublimating refrigerant flowing into the heat exchanger channel, it is proposed that a mixture of refrigerant and a functional carrier flow through the heat exchanger channel, and that the functional carrier is still present as a liquid functional carrier during the sublimation of the refrigerant, which improves heat transfer between the sublimating refrigerant and the heat exchanger body containing the heat exchanger channel.